1. Field of the Invention
The present invention relates to a signal monitor apparatus for use in a video and audio transmission system or the like used in a broadcasting station, for example.
2. Description of the Related Art
FIG. 1 of the accompanying drawings shows an example of a signal monitor apparatus for use in a video and audio transmission system used in a broadcasting station or the like.
In the signal monitor apparatus shown in FIG. 1, a video signal from a video and audio signal source 1 is supplied to a monitor (television monitor) 2 and displayed on a picture screen of the monitor 2 as an image Vi. An audio signal from the signal source 1 is supplied through an amplifier 4 to a speaker 5, from which it is emanated as sounds. The level of the audio signal also is indicated by a level indicator (analog meter) 3.
Broadcasting stations include a plurality of such systems (e.g., main system, sub system and Telop system) and a transmission system for effecting a television broadcasting, thereby forming the transmission system. The level indicator 3 and the speaker 5 are used in the transmission system in order to determine the presence or absence of an abnormality, such as a breaking of wire and a trouble. It is customary that a main system (i.e., system having a main signal source) and a system having a signal source for a Telop (message, such as "WAIT A MINUTE, PLEASE") are used as broadcasting systems. The operator monitors the level indication of the level indicator 3 and the output of the speaker 5. If it is determined by the operator that an abnormality, such as a breaking of wire and a trouble, occurred, then the operator can select a sub system (i.e., system having a sub signal source which generates a signal of the same content as that of the signal supplied from the main signal source). Therefore, even when a wire breaks or trouble occurs in the main system during broadcasting, it is possible to prevent the accident from affecting the broadcast by using the sub system immediately.
If it is determined by the level indicator 3 or the speaker 5 whether or not a breaking of wire or a trouble occurred in the system, then the following serious troubles arise.
It is difficult for the operator to determine on the basis of sounds emanated from the speaker 5 whether or not an abnormality, such as a breaking of wire or a trouble has occurred, as it is substantially impossible for the operator to determine the occurrence of a break or other trouble because the operator cannot tell one sound from other sounds produced from a plurality of speakers used in a plurality of systems at the same place operating at the same time.
Further, it is difficult for the operator to determine by visually confirming the state of the level indicator 3 whether or not an abnormality, such as a wire break or other trouble has occurred, as it is substantially impossible for the operator to determine the occurrence of a wire break or other trouble because the operator must watch a plurality of level indicators at the same place at the same time. By way of example, the operator can watch one or two level indicators at the same place at the same time but cannot watch five systems, i.e., five level indicators simultaneously. Furthermore, since the level indicator indicates the level in a real time fashion, it is substantially impossible for the operator to presume the contents on the basis of index deflection (i.e., index deflection in the case of a meter using an index and the number of photo-diodes in the case of a meter using a plurality of LEDs (light emitting diodes)).
To solve the aforesaid problems, it is proposed that the operator listens to sounds of the speaker of every system or to watch the level indicator of every system by switching the systems one by one with some suitable means, such as a switcher or the like. In this case, the operator should constantly switch the switcher and cannot monitor the all systems simultaneously. If the operator does not monitor all the systems simultaneously, the operator can not monitor systems other than the present system. Furthermore, if the operator switches the system with the switcher, then the operator suffers from increased cumbersome work.
Specifically, it is very difficult for the operator to monitor the system by using the level indicator or the speaker. Also, the operator cannot monitor a plurality of systems at the same time. Furthermore, if the operator intends to monitor the system by switching a plurality of systems with the switcher, then the operator's work becomes cumbersome and complicated.